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 <CALWDO_VHTT4V5GvPFtSZcW5Xce8oTSaLNdNQ1gNd=hyCaBX-yg@mail.gmail.com>
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From:   Alain Michaud <alainmichaud@google.com>
Date:   Wed, 10 Jun 2020 09:33:47 -0400
Message-ID: <CALWDO_Vynv46nYHC-cEb0tL0doDMHzqQG+rCYAi+vRe886earg@mail.gmail.com>
Subject: Re: [PATCH v2] sco:Add support for BT_PKT_STATUS CMSG data
To:     Marcel Holtmann <marcel@holtmann.org>
Cc:     Alain Michaud <alainm@chromium.org>,
        BlueZ <linux-bluetooth@vger.kernel.org>
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On Wed, Jun 10, 2020 at 9:33 AM Alain Michaud <alainmichaud@google.com> wrote:
>
> Hi Marcel
>
> On Wed, Jun 10, 2020 at 4:25 AM Marcel Holtmann <marcel@holtmann.org> wrote:
>>
>> Hi Alain,
>>
>> > This change adds support for reporting the BT_PKT_STATUS to the socket
>> > CMSG data to allow the implementation of a packet loss correction on
>> > erronous data received on the SCO socket.
>> >
>> > The patch was partially developed by Marcel Holtmann and validated by
>> > Hsin-yu Chao
>> >
>> > Signed-off-by: Alain Michaud <alainm@chromium.org>
>> >
>> > ---
>> >
>> > include/net/bluetooth/bluetooth.h |  8 +++++++
>> > include/net/bluetooth/sco.h       |  3 +++
>> > net/bluetooth/af_bluetooth.c      |  3 +++
>> > net/bluetooth/hci_core.c          |  1 +
>> > net/bluetooth/sco.c               | 35 +++++++++++++++++++++++++++++++
>> > 5 files changed, 50 insertions(+)
>>
>> I already had this patch in my tree for testing, but then realized that I gave you a bad example on how to handle this.
>>
>> So we should not use the same constants for CMSG and socket options. Fundamentally the socket semantics use SO_foo for enabling an aux data transmission and they use SCM_bar for the CMSG portion.
>>
>> >
>> > diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
>> > index 3fa7b1e3c5d9..85e6c5754448 100644
>> > --- a/include/net/bluetooth/bluetooth.h
>> > +++ b/include/net/bluetooth/bluetooth.h
>> > @@ -147,6 +147,8 @@ struct bt_voice {
>> > #define BT_MODE_LE_FLOWCTL    0x03
>> > #define BT_MODE_EXT_FLOWCTL   0x04
>> >
>> > +#define BT_PKT_STATUS          16
>> > +
>> > __printf(1, 2)
>> > void bt_info(const char *fmt, ...);
>> > __printf(1, 2)
>> > @@ -275,6 +277,7 @@ struct bt_sock {
>> >       struct sock *parent;
>> >       unsigned long flags;
>> >       void (*skb_msg_name)(struct sk_buff *, void *, int *);
>> > +     void (*skb_put_cmsg)(struct sk_buff *, struct msghdr *, struct sock *);
>> > };
>> >
>> > enum {
>> > @@ -324,6 +327,10 @@ struct l2cap_ctrl {
>> >       struct l2cap_chan *chan;
>> > };
>> >
>> > +struct sco_ctrl {
>> > +     u8      pkt_status;
>> > +};
>> > +
>> > struct hci_dev;
>> >
>> > typedef void (*hci_req_complete_t)(struct hci_dev *hdev, u8 status, u16 opcode);
>> > @@ -350,6 +357,7 @@ struct bt_skb_cb {
>> >       u8 incoming:1;
>> >       union {
>> >               struct l2cap_ctrl l2cap;
>> > +             struct sco_ctrl sco;
>> >               struct hci_ctrl hci;
>> >       };
>> > };
>> > diff --git a/include/net/bluetooth/sco.h b/include/net/bluetooth/sco.h
>> > index f40ddb4264fc..7f0d7bdc53f6 100644
>> > --- a/include/net/bluetooth/sco.h
>> > +++ b/include/net/bluetooth/sco.h
>> > @@ -46,4 +46,7 @@ struct sco_conninfo {
>> >       __u8  dev_class[3];
>> > };
>> >
>> > +/* CMSG flags */
>> > +#define SCO_CMSG_PKT_STATUS  0x0001
>> > +
>> > #endif /* __SCO_H */
>> > diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
>> > index 3fd124927d4d..d0abea8d08cc 100644
>> > --- a/net/bluetooth/af_bluetooth.c
>> > +++ b/net/bluetooth/af_bluetooth.c
>> > @@ -286,6 +286,9 @@ int bt_sock_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
>> >               if (msg->msg_name && bt_sk(sk)->skb_msg_name)
>> >                       bt_sk(sk)->skb_msg_name(skb, msg->msg_name,
>> >                                               &msg->msg_namelen);
>> > +
>> > +             if (bt_sk(sk)->skb_put_cmsg)
>> > +                     bt_sk(sk)->skb_put_cmsg(skb, msg, sk);
>> >       }
>> >
>> >       skb_free_datagram(sk, skb);
>> > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
>> > index 51d399273276..7b5e46198d99 100644
>> > --- a/net/bluetooth/hci_core.c
>> > +++ b/net/bluetooth/hci_core.c
>> > @@ -4549,6 +4549,7 @@ static void hci_scodata_packet(struct hci_dev *hdev, struct sk_buff *skb)
>> >
>> >       if (conn) {
>> >               /* Send to upper protocol */
>> > +             bt_cb(skb)->sco.pkt_status = flags & 0x03;
>> >               sco_recv_scodata(conn, skb);
>> >               return;
>> >       } else {
>> > diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c
>> > index c8c3d38cdc7b..f6b54853e547 100644
>> > --- a/net/bluetooth/sco.c
>> > +++ b/net/bluetooth/sco.c
>> > @@ -66,6 +66,7 @@ struct sco_pinfo {
>> >       bdaddr_t        dst;
>> >       __u32           flags;
>> >       __u16           setting;
>> > +     __u32           cmsg_mask;
>> >       struct sco_conn *conn;
>> > };
>> >
>> > @@ -449,6 +450,15 @@ static void sco_sock_close(struct sock *sk)
>> >       sco_sock_kill(sk);
>> > }
>> >
>> > +static void sco_skb_put_cmsg(struct sk_buff *skb, struct msghdr *msg,
>> > +                          struct sock *sk)
>> > +{
>> > +     if (sco_pi(sk)->cmsg_mask & SCO_CMSG_PKT_STATUS)
>> > +             put_cmsg(msg, SOL_BLUETOOTH, BT_PKT_STATUS,
>>
>> This needs an extra BT_SCM_PKT_STATUS constant.
>
> Since we don't have this name space defined yet, I'm assuming I just start with 01 for this.
>>
>>
>> > +                      sizeof(bt_cb(skb)->sco.pkt_status),
>> > +                      &bt_cb(skb)->sco.pkt_status);
>> > +}
>> > +
>> > static void sco_sock_init(struct sock *sk, struct sock *parent)
>> > {
>> >       BT_DBG("sk %p", sk);
>> > @@ -457,6 +467,8 @@ static void sco_sock_init(struct sock *sk, struct sock *parent)
>> >               sk->sk_type = parent->sk_type;
>> >               bt_sk(sk)->flags = bt_sk(parent)->flags;
>> >               security_sk_clone(parent, sk);
>> > +     } else {
>> > +             bt_sk(sk)->skb_put_cmsg = sco_skb_put_cmsg;
>> >       }
>> > }
>> >
>> > @@ -846,6 +858,18 @@ static int sco_sock_setsockopt(struct socket *sock, int level, int optname,
>> >               sco_pi(sk)->setting = voice.setting;
>> >               break;
>> >
>> > +     case BT_PKT_STATUS:
>> > +             if (get_user(opt, (u32 __user *)optval)) {
>> > +                     err = -EFAULT;
>> > +                     break;
>> > +             }
>> > +
>> > +             if (opt)
>> > +                     sco_pi(sk)->cmsg_mask |= SCO_CMSG_PKT_STATUS;
>> > +             else
>> > +                     sco_pi(sk)->cmsg_mask &= ~SCO_CMSG_PKT_STATUS;
>> > +             break;
>> > +
>> >       default:
>> >               err = -ENOPROTOOPT;
>> >               break;
>> > @@ -923,6 +947,7 @@ static int sco_sock_getsockopt(struct socket *sock, int level, int optname,
>> >       int len, err = 0;
>> >       struct bt_voice voice;
>> >       u32 phys;
>> > +     u32 pkt_status;
>>
>> Lets follow the example of SO_TIMESTAMP and use int here and convert it to a bool meaning. Since the BT_PKT_STATUS really is just suppose to enable / disable sending the packet status.
>
> I get that SO_TIMESTAMP uses a signed integer here, but I'm not quite sure what benefit it provides, especially when simply using it as a boolean value.
>>
>>
>> >
>> >       BT_DBG("sk %p", sk);
>> >
>> > @@ -969,6 +994,16 @@ static int sco_sock_getsockopt(struct socket *sock, int level, int optname,
>> >                       err = -EFAULT;
>> >               break;
>> >
>> > +     case BT_PKT_STATUS:
>> > +             if (sco_pi(sk)->cmsg_mask & SCO_CMSG_PKT_STATUS)
>> > +                     pkt_status = 1;
>> > +             else
>> > +                     pkt_status = 0;
>> > +
>> > +             if (put_user(pkt_status, (u32 __user *)optval))
>> > +                     err = -EFAULT;
>> > +             break;
>> > +
>> >       default:
>> >               err = -ENOPROTOOPT;
>> >               break;
>>
>> Regards
>>
>> Marcel
>>